title for learn-about section on whelks & relatives in A SNAIL'S ODYSSEY
  Predators & defenses
  black dot

Noxious secretions

  This section on predators & defenses is divided into topics of noxious secretions considered here, and


SHELL SIZE & THICKNESS, considered in other sections.
  black dot
Research study 1

photograph of Oregon triton Fusitriton oregonensis courtesy Dave Cowles, Walla Walla University, WashingtonThe snail Fusitriton oregonensis appears to have few or no natural predators.  One reason for this may be a bitter-tasting flesh, described by one California researcher as having a strong after-taste of iodine.  When placed in a frying pan the flesh apparently emits an “objectionable odour”.  Further research may be justified.  Talmadge 1975 Bull Am Malacol Union Inc 49: 59. Photograph courtesy Dave Cowles, Walla Walla University, Washington www.wallawalla.

Neither the spikey adornments, nor the objectionable
odour stops a variety of anemones and sea squirts
from taking up residence on the shell of this
Oregon triton Fusitriton oregonensis 0.75X

  black dot
Research study 2

Toxic or inhibitory secretions from the hypobranchial1 gland of west-coast Nucella spp. have not been demonstrated, but can be inferred from work on other species.  In the European Nucella lapillus, for example, extracts2 of the gland produce marked relaxation or paralysis of isolated heart muscles in mussels Mytilus edulis.  Similar studies appear not to have been done for any west-coast species of whelk3Andrews et al. 1991 J Mollusc Stud 57: 136.

NOTE1  the pharmacologically active substance in muricids including Nucella and Thais species appears to be a mix of urocanylcholine, known as murexine, and/or other choline esters.  Roseghini et al. 1970 Eur J Biochem 12: 468

NOTE2  the hypobranchial gland is found in many or all gastropods, and is present in all muricids.  It is a conspicuous, folded glandular structure located on the roof of the mantle cavity.  In Nucella spp. the secretion is a yellow or white viscid slime, but in related muricids such as Murex spp. and Purpura spp., it is purple-coloured, and the former species represents the source of Tyrian purple dye used by ancents.  Nowadays, the chemical structure of Tyrian dye is known and it is readily synthesised in the laboratory. In past times it was a highly valued and sought-after commodity, and was briskly traded throughout the Mediterranean region.  Until recently there has been no known function for Tyrian purple and many researchers regard it as an artifact or waste product.  However, precursors of purple pigments similar to those isolated from the hypobranchial glands are reported to be incorporated into egg capsules in several species of Australian muricids, where they are thought to play a defensive role against microbial infection. The fact that not all muricids incorporate these precursors into their eggs, yet have them in their hypobranchial glands, could imply alternate, possibly defensive, functions for them. Benkendorff et al. 2004 Invert Reprod Dev 46: 93

NOTE3 however, similar defensive functions are described for west-coast Calliostoma canaliculatum: see LEARN ABOUT ABALONES & RELATIVES: PREDATORS & DEFENSES: CHEMICAL DEFENSES

  black dot